Capacitors are widely used in many terminal electronic devices, such as a touch sensor used for touch control on a display screen of a terminal device. During use of a capacitor, it is essentially required to measure and analyze capacitance of the capacitor. Currently, self-capacitance detection has become a very important measurement and analysis method.
However, self-capacitance tends to be relatively large, and the existing self-capacitance detection method has lower sensitivity when the self-capacitance is large. In addition, a cancel capacitor for improving the sensitivity is relatively large and cannot be integrated, and a cost of the cancel capacitor is also too high. Further, an increase in self-capacitance causes the sensitivity of the existing self-capacitance detection method to be lower, and a capacitance value cannot be correctly detected.
A differential circuit can be used to enhance the capacitance detection sensitivity to some extent. However, there still exists a noise signal such as 1/f noise and low frequency noise, affecting a signal-to-noise ratio of an output signal. Therefore, a low-noise differential circuit is urgently needed.